Quantification of cationic anti-malaria agent methylene blue in different human biological matrices using cation exchange chromatography coupled to tandem mass spectrometry

Dried blood spot sampling in combination with LC‐MS/MS for quantitative analysis of small molecules

“…The blood sample can also be applied with a calibrated pipette onto the sampling paper/card, thus avoiding potential variability in blood samples due to hematocrit eff ect, blood volume infl uence, possible uneven distribution of blood on the card/paper and other sampling errors (Alfazil and Anderson, 2008;Burhenne et al, 2008;Garcia Boy, 2008;Koal et al, 2005). The pipette tip should be a few millimeters above the card/paper.…”

“…However, the drying time depends on the type of paper/card and the blood volume applied (Hoogtanders et al, 2007;Koal et al, 2005;Spooner et al, 2009). The samples should not be heated, stacked or allowed to touch other surfaces, and should be kept away from direct sunlight or daylight if needed (Burhenne et al, 2008). Moisture might aff ect the quality of the blood samples on the card/paper by inducing bacterial growth, altering extraction effi ciency during analysis or facilitating degradation of unstable analytes.…”

“…The acceptable LLOQ is defi ned as the lowest analyte concentration that gives accuracy within ±20% (bias) of the nominal value and precision ≤20% (CV) from six replicates for a predefi ned dynamic range. Considering the limited blood volume taken from a punch, a larger punch or multiple punches make the lower concentration of analyte measurable (Alfazil and Anderson, 2008;Garcia Boy et al, 2008;Burhenne et al, 2008;Gempel et al, 2000;Higashi et al, 2008;la Marca et al, 2008bla Marca et al, , 2009Liang et al, 2009). On the other hand, a larger punch from a small spot might result in a better reproducibility and a small punch from a large area might be one of the sources of poor assay precision due to the chromatographic eff ect (Hoogtanders et al, 2007).…”

“…On the other hand, ion suppression is often evaluated during method development by post-column infusion of the analyte and/or IS neat solutions while analyzing blank DBS sample extract from six blood lots. As long as there is no signifi cant decrease or increase of the instrument (MS/MS) response in the retention time region of the target analyte and/or IS from the blank DBS sample injection, one could assume that there is no apparent ion suppression or enhancement (Burhenne et al, 2008;Damen et al, 2008;ter Heine et al, 2008ter Heine et al, , 2009aWilhelm et al, 2009;van der Heijden et al, 2009).…”

“…As listed in Table 1, DBS-LC-MS/MS has been increasingly employed in clinical study and therapeutic drug monitoring for the analysis of a wide spectrum of drug molecules, including antipyretic (Spooner et al, 2009), antitussive (Liang et al, 2009), antimalarial (Burhenne et al, 2008), anticonvulsant (la Marca et al, 2009, antiretroviral (Koal et al, 2005;ter Heine et al, 2008ter Heine et al, , 2009a, immunosuppressant (Cheung et al, 2008;Hoogtanders et al, 2007;Wilhelm et al, 2009), antiepileptic (la Marca et al, 2008b and vinca alkaloids (Damen et al, 2009), and in monitoring drug abuse (Henderson et al, 1997;Garcia Boy et al, 2008). Because DBS samples could be collected by patients themselves or their guardians with minimum training, this opens up the possibilities of collecting clinical pharmacokinetic samples not only from various in-patients, but also from out-patients, especially those from remote areas (Burhenne et al, 2008).…”